Fixing unit for photocopy machines



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FIXING UNIT FOR PHOTOCOPY MACHINES Filed July 11, 1962 4 Sheets-Sheet 4Q I I 9 ISO I 22 so A w 1% m United States Patent 3,159,735 FIXING UNITFOR PHGTOCUPY MACHINES Burton D. Eisner and George C. Kent, HighlandPark, Edwin A. Larson, Chicago, and Meyer L. Sugarmau, Jr., Glencoe,IlL, assignors to American Photocopy Equipment Company, Evanston, Hit, acorporation of Illinois Filed July 11, 1962, Ser. No. 269,122. Claims.(Cl. 219-347) The present invention relates to electrophotographicprinting and, more particularly, to an improved means for fixing adeveloped image to the copy sheet.

The electrophotographic printing process employed in olfice photocopymachines and the like commonly involves the steps of uniformly chargingan electrographic sheet, exposing the sheet to produce a latent imagethereon with dissipation of the charge from the light-struck areas,development of the image by applying a pigmented powder or toner whichtends to adhere selectively to the charged areas, and then fixing thepowder in place by heat. The powder conventionally includes a minorproportion of heat settable resin which, upon being heated, causes thepowder to adhere to the surface of the sheet. A machine of this type isdisclosed in Sugarman US. Patent 3,088,366 which issued on May 7, 1963.However, one of the problems encountered in known types of photocopymachines is either that fixing is incomplete or uneven resulting insmeared or imperfect copies or that the temperature tends to build upwhen the machine is operated for long periods, thereby running the riskof scorching. Moreover, prior devices have been subject to malfunctionby reason of buckling of the sheet, particularly the leading edgethereof as the sheet passes into the fixing station and before the sheetis nipped by the final expeller rollers so that a copy sheet may becomehung up within the machine to produce a jam and a possible fire hazard.The prior Sugarman application embodied one solution to this problem; animproved arrangement is described and claimed herein.

Accordingly it is an object to provide an improved fixing unit for anelectrophotographic machine which is more reliable than prior fixingarrangements and which is capable of fixing the powder image uniformlyand to the correct degree, tree of blemish or imperfection, regardlessof how long the machine has been operating and Without risk of scorchingand overheating. It is a related object to provide a fixing unit of theabove type in which each sheet is passed through the unit and positivelydischarged and in which there is no danger of a sheet buckling orbecoming hung up within the fixing unit, thereby obviating the nuisanceand hazard which results when a sheet catches fire. In this connectionit is also an object to provide a fixing unit capable of reliablyhandling copy sheets which are thinner than those which may be handledby conventional machines, even light weight tissue stock. At theopposite extreme, sheets of double weight or card stock may beefiiciently handled.

It is an other object to provide a heat fixing unit for a photocopymachine which is highly efiicient and which effectively utilizes theradiant heat from the heat lamp with the radiant heat being concentratedin a novel fashion upon the sheet being acted upon. It is a relatedobject to provide a fixing unit having convenient means for adjustingthe radiant heat source relative to the sheet so that the radiant energyis focused upon the sheet along a narrow transverse strip and which doesnot require that a large area of the sheet be acted upon simultaneouslyby the heat source. It is an object to provide novel adjusting means forcontrolling the peak temperature of the sheet. Nevertheless it is afeature of the machine that the focusing adjustment is non-critical andthat the sheet may depart from the fixing plane, as may happen at theleading edge of the sheet and prior to nipping by the expeller 3,159,735Patented Dec. 1, 1964 rollers, without sacrifice of reliability. It isone of the objects to provide a fixing unit which is capable of actinguniformly over the entire length of the sheet from the leading edge tothe trailing edge.

It is a detailed object to provide apparatus of the above type in whichthe source of radiant energy is at the back of the sheet for avoidanceof hot spots in the pigmented areas.

It is still another object of the present invention to provide a fixingunit having novel and etficient means for carrying away the excess orunwanted heat, and particularly the non-radiant heat components, withoutreducing the radiant component of heat energy which is primarilyeffective to accomplish the fixing so that the environment of the sheetis maintained at a safe low temperature and so that the casing of themachine becomes no more than slightly Warm to the touch even duringextended periods of operation.

It is a further object of the present invention to provide a fixing unitwhich is easy to service and in which it is possible either to inspectthe fixing region or to inspect or replace the fixing lamp at the frontof the machine simply by swinging the lamp and reflector assemblydownwardly about a horizontal axis. It is a more detailed object toprovide a lamp and reflector assembly which includes an integral heatduct but which does not require that such duct be disconnected when anassembly is swung to its exposed, or servicing, position. It is an otherdetailed object to provide for immediate and complete access to the lampand fixing region by swinging the lamp assembly out of the way butwithout, however, disturbing the focusing adjustment of the lampassembly.

Finally, it is an object of the present invention to provide a fixingunit which consists of a minimum number of simply formed pants,primarily extrusions, and which may be constructed, assembled andmaintained at minimum expense.

Other objects and advantages of the invention will become apparent uponreading the attached description and upon reference to the drawings inwhich:

FIGURE 1 is a simplified vertical section of a photocopy machineemploying the present invention and with the stationary air duct brokenaway to reveal the fixing station.

FIG. 2 is a horizontal fragmentary section showing the fixing unit andtaken along line 22 in FIG. 1.

FIG. 3 is a fragmentary View showing the disengagement of the adjustingpins required to swing the lamp and reflector assembly into its exposed,servicing position.

FIG. 4 is a fragmentary view showing one of the lamp mounting brackets.

FIG. 5 is a fragment showing the left hand focusing mechanism.

FIG. 6 is a transverse section taken through the fixing unit along theline 6-6 in FIG. 2.

FIG. 7 is a face view at reduced scale of one of the wire guardingmembers.

FIG. 8 is a transverse section similar to FIG. 6 but showing analternative form of sheet guiding means.

FIG. 9 is a horizontal section, foreshortened and with portions brokenaway taken along the line 99 in FIG. 8.

FIG. 10 is a transverse vertical section taken along the line 10-10 inFIG. 8.

While the invention has been described in connection with certainpreferred embodiments, it will be understood that we do not intend to belimited to the particular embodiments shown but intend to cover thevarious alte native and equivalent constructions falling within thespirit and scope of the appended claims.

Turning now to FIG. 1 of the drawings, an electrophotographic copyingmachine intended for oifice use has a frame 11, a base 12 and a housing13. At the front of the housing two inlet slots are provided, a firstslot 14 for the original and a second slot 15 for the copy sheet, withthe two sheets, indicated at 16, 17, being fed in together, face toface. The sheets are separated and the copy sheet passes through acharging unit 18 where the face of the sheet acquires an overall staticelectric charge. The sheet is coated with zinc oxide or similar materialhaving the ability to dissipate charge in areas which are selectivelystruck by light.

The original 16 is fed into an illuminating station 21 at the same timethat the copy sheet 17 is fed into an exposing station 22. Light from asource 23 illuminates the original, with the image thereof beingreflected by a mirror and lens assembly 24 onto the moving copy sheetand with the speed of the original corresponding exactly to the speed ofthe copy sheet. Subsequently the original is discharged into a returnchute 25 while the copy sheet is conveyed upwardly by transport rollers26, 2'7 into a developing unit 28 and fixing unit 39 for discharge upona tray 31 at the top of the machine.

For details of the developing unit 28 reference is made to copendingapplication Ser. No. 211,779, filed July 23, 1962. It will sufiice tosay that the non-exposed areas on the copy sheet retain theirelectrostatic charge and hence attract toner particles. It is thefunction of the fixing unit 36 to heat the sheet with the tonerparticles thereon so that the particles, which include a heat-setbinding agent adhere to the surface of the sheet, thereby to produce apermanent copy. In the paragraphs of description which follow, attentionwill be focused upon the novel fixing unit which forms the subject ofthe present in vention.

For the purpose of guiding the copy sheet 17 upwardly through the fixingunit 30 for positive discharge, the copy sheet is passed from thedeveloping unit 28 straight up along a fixing plane and into the nip ofexpeller rollers 36, 37 which are topped by a deflector 38. While themeans for driving the rollers 26, 27 and 36, 37 is not shown, it will beunderstood that the rollers are powered from the main driving motor viaany desired belt or gearing arrangement producing a constant andpredetermined surface speed.

Spaced from the sheet 17 and extending transversely with respect to themovement of the sheet is a lamp and reflector assembly 40. The reflector41 is of C shape having an internal reflecting surface 42 terminating inlips 43, 44. The reflector is made of metal having good heat conductingproperties such as aluminum and is of relatively massive construction,as shown, terminating in an enlarged base 45 to provide a good heatconduction path. The reflecting surface may be gold plated if desired.

Enclosed within the reflecting surface 42 is a heat lamp 54) in the formof a thin tube having sockets 51, 52 at its ends. The sockets extend theends of the reflector 41 as shown in FIG. 2. The lamp is preferably madeof quartz having a tungsten filament extending longitudinally thereinand may be either evacuated or gas filled. The filament is preferablyoperated at a high temperature, on the order of l800-2400 K. with apower dissipation of 650 watts. This not only produces radiation withinan optimum range for absorption by the image on the copy sheet but alsotend to minimize warm-up time. In the present design of machine thewarm-up time is on the order of nine second or less so that there is nodelay in putting the machine in operation.

In accordance with one of the aspects of the present invention, thereflecting surface 42 is elliptical and the lamp is so positioned thatthe filament coincides with one of the elliptical foci 53 while theother elliptical focus 54 substantially coincides with the fixing plane.For mounting the lamp in place, mounts 55, 56 are provided for engagingthe sockets 51, 52. Taking the mount by way of example (FIG. 4) it willbe seen that it is in the form of a C-shaped plate of metal having acentral recess 57 bridged by a releasable spring clip 58 and tilanchored to the ends of the reflector member upon pedestals 59.

It will be appreciated by one skilled in the art that with thereflecting surface 42 in elliptical form having foci 53, 5 positioned asshown, the radiant energy will be focused along the focus 54, i.e.,along a line or relatively narrow fixing ban extending transversely onthe sheet 17. As a result of this concentration of radiant energy, theregion of high temperature is localized so that the temperature at thefixing band is much higher than the temperature elsewhere in the fixingunit. Stated in other terms, the present arrangement enables a hightemperature to be achieved along a narrow band on the paper to raise theparticles of toner to fusing temperature while the temperature of thefixing unit as a whole is kept at a low level. This is to be contrastedwith prior arrangements which rely primarily upon oven effect, i.e.,upon keeping a relatively large region within the fixing unit at thefusing temperature.

In accordance with one of the aspects of the invention there isprovided, aligned with and directly opposite the reflecting surface 42,a heat reflecting member 62 for confining the heat and for reflectingback at least a portion thereof. The nature of the surface is notcritical although polished metal is preferred. The member 62 serves toreflect back the longer, penetrating rays of radiant energy in thedirection of the sheet but also serves, in the absence of the sheet toreflect back cumulatively the energy directly radiated by the lamp sothat the device comes up to operating temperature promptly after thecurrent is turned on. In a practical design of machine such initialWarm-up period may be on the order of ten seconds. Moreover, because ofthe multiple reflection which takes place the fixing region is largelyfree of high temperature gradients which might tend to cause curling ofthe advancing sheet. In order to prevent unwanted scatter of the radiantenergy outside of the fixing region, additional heat absorbing walls areprovided above and below the reflector 42 and mirror 62. The heatabsorb-ing walls associated with the reflector and indicated at 63, 64are preferably formed integral with the reflector body, for example, aspart of the same extrusion, so as to provide a good heat conductingpath. The heat absorbing walls 65, 66 lying above and below the mirror62 are also made of good conducting metal with means being provided forefliciently carrying. away the absorbed heat.

It is one of the features of the present construction that means areprovided for preventing contact between the sheet and any flat surfacewhich may serve as a drag upon the sheet and which, therefore, mighttend to buckle the leading edge thereof before such edge is nipped bythe expeller rollers. Thus there is provided in front of the reflectormember 41 a guard 70 which consists of spaced generally vertical wireslying in a plane and secured top and bottom to headers 71, 72,preferably by welding. To maintain the wire guard 76 in position, thebottom header is fitted into notches 73 in the frame plates While theupper header is secured by a spring clip 74. As will become apparent,this enables the guard to be quickly removed for access to the fixingregion. For the purpose of preventing contact between the sheet and theflat surfaces 62, and 66 on the other side, a guard 8i) is providedwhich consists of spaced generally vertical wires secured top and bottomto headers 81, 82. The lower header is received in notches 83 in theframe and the ends of the upper header are received in holes 84 formedin the frame members 114, 114a which will be described in detail at alater point. The wires are preferably profiled as shown in FIG. 6projecting forwardly at the upper end to guide the leading edge of thecopy sheet into the nip of rollers 3-6, 37. It will be noted that thewires are bentbackwardly to provide clearance opposite the lamp 5t)which is the region of highest temperature. By the time that the sheetreaches the point 85, it is sufficiently cool.

so that contact with the guard wires will not deface the pigmented sideof the sheet.

While it has been stated above that the wires forming the guards 70, 80are generally vertical, it is preferred to arrange the wires inherringbone pattern as set forth in FIG. 7, with the wires divergingsomewhat outwardly and upwardly with respect to the center line. It isfound that this tends to keep the copy sheet flat, particularly whereone of the corners of the advancing edge of the copy sheet has beenturned over or is dog-cared and might, therefore, become caught on oneof the wires or headers. The action of the diverging guard wires is totend to straighten out the corner, keeping it flat in the plane of thesheet ready for engagement with the nipping rollers. Equally important,keeping in mind that the wires are in the path of radiation, the heattransferred from the Wires to the sheet tends to be distributed over thesurface of the sheet rather than being concentrated along narrow paths.

If desired and without departing from the invention, the guard 89 may bedispensed with and the paper may be held forwardly by an air blast froma series of horizontally arranged holes directly opposite the heatsource; however, this requires a corresponding increase in capacity ofthe blower which is used for cooling purposes. If desired, also, avacuum may be drawn in the C-shaped reflector by a vacuum line.

While a copy sheet will normally remain in flat condition and will moveupwardly along the fixing plane 35, it does sometimes happen that thepaper has, or acquires curvature. This may happen for example where thesheets have been stored in a damp environment and where suddensubjection to heat will produce differential effects on the oppositesides of the sheet causing the leading edge to curl in one direction orthe other. It is one of the features of the present invention thatmovement of the sheet through the fixing region is entirely unobstructedso that there is no tendency for the sheet to buckle with localizedguiding edges being provided so that even in the case where the paperacquires a serious curl contact is so limited that the curl is keptunder control, with minimum drag, until such time as the leading edge isengaged by the expeller rollers. Since the drag upon the advancingsheet, regardless of whether it is straight or curled, is minimum, thepresent fixing unit is able to handle sheets which are much thinner thancan be accommodated in conventional fixing units, even sheets of tissueweight.

In accordance with the present invention, parallel air ducts areprovided on the opposite sides of the fixing unit and having closethermal coupling to the reflector member, mirror and associated heatabsorbing surfaces so that unwanted heat is efilciently conducted awayfrom the fixing unit. In the present instance the ducts indicated at 86,86a are of rectangular cross section having alined inlets 87, 87a. Forsupplying air to the inlets a blower 83 is provided, coupled to theducts by a conduit 88a. The conduit terminates in outlets 89, 89a whichare, as shown in FIG. 2, alined with the duct inlets.

In order to provide close thermal coupling between the reflector member41 and the air flowing through the adjacent duct, a heat sink member 90is provided (FIG. 6) which is in flat face-to-face contact with the base45 of the reflector and which has integral heat conducting fins 91spaced the entire width of the duct. For the purpose of securing thereflector member 41 to the member 90 screws 92 are used.

At the other side of the fixing unit there is a second heat sink member100 having fins 101. Because of the close thermal coupling provided bythe construction described above, it will be apparent that the heatwhich is conducted by the reflector member including the scatterradiation employed by the absorbing walls 63-66, is not allowed to buildup but is immediately withdrawn into the air stream.

In order to maintain the temperature of the expeller rollers 36, 37,especially the roller 37 which contacts the face of the sheet, at a safelevel, and considering that the rollers are in the direct path of upwardheat convection from the fixing region, an auxiliary air vent 185 isprovided along the upper edge of the duct 82. The upper portion of theduct 82 is preferably blocked at its end by a plug 106 of sponge plasticor the like in order to develop sufllcient back pressure to produce aforceful jet of air. It will be apparent to one skilled in the art thata partial barrier may be provided along the length of the upper airchamber as may be necessary to cause the air to be emitted from the ventat approximately the same velocity along its entire length. The air fromthe vent serves the additional purpose of blowing the leading edge ofthe sheet into a position where it is more readily engaged by the nip ofthe expeller rollers.

In accordance with an aspect of the present invention, means areprovided for bodily moving the reflector 41, and the lamp mounted withinit, toward and away from the fixing plane 35 thereby to achieve avariation in the peak temperature to which the passing sheet issubjected. This is accomplished in the present instance by providingadjustable mounts having a pin and cam at each end between the reflectorand lamp assembly and the frame of the machine. Referring to the mount110 at the left hand end of the reflector assembly (FIGS. 2, 3 and 5),it will be noted that it is in the form of a bracket 111 which issecured to the member 90 by screws 112. Means are provided for pivotingthe lower end of the bracket to the frame of the machine so that thereflector assembly may be rocked through a limited range of adjustment.This is accomplished by a pivot pin 113 which is secured to the framebracket 114 of the machine and which engages an opening 115.

Adjustment is provided by a pin and cam connection which, in the presentinstance, includes a pin mounted on the frame bracket 114 previouslyreferred to and which engages a cam slot 121 (FIGS. 5, 6). For thepurpose of adjusting the earn, the cam slot 121 is formed in a slidemember 125 which is mounted on the supporting bracket 111 by pin andslot connections indicated at 126, 127. A finger tab 128 is provided atthe upper end of the slide. It will be apparent that pressing down uponthe finger tab 128 causes the pin 120 to slide to the top end of the camsurface 121 thereby roclc'ng the reflector assembly outwardly and awayfrom the sheet. A corresponding bracket and adjusting arrangement Him isprovided at the other end of the member 90, with corresponding partsindicated by reference numerals with the subscript a. Normally theadjustment of the slides 125, 125a will be kept in step with one anotherso that the reflector and lamp are kept parallel to the sheet.Adjustment of the slides may be either done as a factory operation ormay be done at the time that the machine is installed in place with thesetting depending in part on line voltage conditions at the place ofuse. By positional adjustment of the reflector the radiant energy may befocused onto a narrow transverse band on the paper or may bedeliberately thrown out of focus so that the radiant energy isdistributed over an area with corresponding reduction in temperature. Ithas been found that the mechanical adjustment provides precisetemperature con trol more conveniently and at less cost than when usingvariable resistors or the like.

While it is true that the leading edge of the sheet may not fallprecisely on the fixing plane 35, nevertheless it is found in practicethat the sheet is kept sufiiciently close to the plane by the guardwires 70 and 80 so that adequate and reliable fixing is achieved at theleading edges and trailing edges of the sheet as Well as over thecentral portion.

In accordance with a further aspect of the present invention means areprovided for disengaging the reflector and lamp assembly 40 so that thesame may be swung forwardly and downwardly to expose the lamp forservicing wit-hout upsetting the adjustment of the focus and withoutrequiring any disconnection of the air ducts. This is accomplished inthe present instance by providing a slip joint at the pivot pins 113,113a permitting the reflector and lamp assembly to be moved endwise forsimultaneously disengaging the pins 120, 120a which cooperate with thecam adjusting slots 121, 121a. Thus, as it will be noted in FIG. 2, thepivot pin 113 is extended to the left and the pin 113a is somewhatelongated. In order to bias the reflector and lamp assembly to itsnormal pin engaging position, a coil spling 130 surrounds the pin 113and is held captive by a knob 131 on the end of the pin. To unseat thecam surfaces from the adjusting pins, leftward axial pressure is appliedto the duct 8% (see FIG. 3) compressing the spring 131? and causing theslots 121, 121a to move endwise out of engagement with the pins 120,1219a which are shorter than the pivot pins 113, 113a, permitting thereflector and lamp assembly to be rocked forwardly about its pivot axis,using the knob 81a, through the position indicated by the dotdash linesin FIG. 6. This exposes the lamp 513 for inspection and replacement. Toreplace the lamp, the spring clips 58 which engage the lamp sockets aresimply unhooked so that a new lamp may be readily inserted. Replacingthe lamp does not require refocusing since the lamp filament isautomatically positioned. at the elliptical focus. Access may be had tothe fixing region simply by unhooking the spring clip 74 from the wireguard 70. These operations are simply reversed to reassemble the unit.Moving the reflector unit back in place reestablishes an air connectionbetween the blower and the duct 86 (F1612).

It is one of the features of the above construction that the radiantheat from the lamp and elliptical reflector is applied to the back ofthe sheet. It is found that this produces more even heating over theregion of focus since the rate of absorption of the heat issubstantially the same over each unit of the exposed area. This is to becontrasted with fixing units which illuminate the face of the sheet andwhere the temperature may vary widely between the heat-absorbingpowdered areas and non-powdered areas. As a result of the backillumination combined with the other features described above, hot spotsare completely avoided.

In a typical automatic operating cycle the lamp is turned onapproximately ten seconds before the arrival of the copy sheet. Duringthis period the radiation is unobstructed and, because of the mirror 62and the resulting multiple reflection, there is a build up in theradiation intensity bringing the temperature within the fixing unitimmediately up to the operating level. Any scatter radiation iscontrolled by the walls 63-66 so that radiation is confined to thefixing region. When the leading edge of the sheet moves into the fixingunit under the urging of rollers 26, 27, it will tend to follow thefixing plane 35, but in the event that the paper tends to curl orbuckle, the guide members 7t), 89 on each side insure that the paper iskept in close proximity to the fixing plane. Since any contact betweenthe sheet and the machine takes place along localized edges, drag uponthe paper is minimized so that there is no danger of a sheet bucklingwithin a fixing region. Any contact between the guard St) and the faceof the sheet will, in a practical case, occur at the upper end of theguard after the image has already been fixed in place so that there isminimum risk of marring the copy. The rollers 36, 37 are preferablyoperated at a surface speed which is just slightly greater than that ofthe rollers 26, 27, on the order of one percent, to take up any curl orslack. Preferably the biasing force between the upper rollers 36, 37 isless than that at the lower rollers so that relative slippage may takeplace. As soon as the leading edge is nipped between the rollers 36, 37,the remainder of the sheet is positively maintained in the fixing plane.

Since the heat is concentrated along a narrow band in the region offocus 5% it is not necessary to maintain the entire fixing unit at hightemperature. Because of this and because of the efiicient withdrawal ofunwanted heat through the heat sinks for transfer to the cooling air,the temperature of the fixing unit is maintained at a low level. Inshort, the machine may be operated substantially below the temperaturelevel at which scorching or charring will take place and there is nodanger of a sheet catching on fire. This is true even in the unlikelyevent that the expeller roller drive is interrupted. The latter has beenfound to produce simple, localized charring along the narrow band at thefocal point and without actual ignition of the sheet.

While the sheet guiding means shown in FIGS. 5, 6 and 7 constitutes aworkable arrangement having a number of important advantages over theprior art, an alternative arrangement having certain additionaladvantages is set forth in FIGS. 8, 9 and 10. In these figurescorresponding reference numerals have been employed, where applicable,with subscript a. For the purpose of preventing the leading edge of asheet, or the body portion thereof, from approaching too closely to thesource of heat, particularly where the sheet has any tendency to curl orbuckle, a guard 76a is employed consisting of a plurality of spaced,generally vertical wires lying in a plane and secured at top and bottomto headers 71a, 72a respectively. The bottom header 72a may be securedin position by any desired means, for example, in notches formed in theframe plates, as in the case of the previous embodiment. The upperheader is supported in place by a spring clip 74a consisting of twoportions, one at each end of the assembly to permit easy movement.

In accordance with one of the aspects of the present invention aplurality of loosely mounted discs or rollers are provided at the lowerend of the guard 70a for the purpose of engaging the leading edge of thesheet for guiding the same into the fixing region and for maintainingthe body of the sheet in position, with the sheet in the region of thefixing plane, as the sheet is propelled upwardly. We prefer to use discs14% mounted on a shaft 141 which shaft is mounted in extensions formedon a supporting member 55a or by any other desired means. The discs arespaced at intervals along the shaft and in a typical chain a total ofsix or more discs may be used.

To enable mounting of the discs so that the periphery thereof lies in adesired sheet guiding path and to position the discs as closely adjacentthe lower end of the guard 7th; as possible, the shaft 141 which carriesthe discs is mounted, as shown, behind the lower heat-absorbing wall orapron 64a, with the discs projecting through clearance slots 142 formedtherein. The slots 142 also serve the purpose of guiding and maintainingproper spacing between the adjacent discs. Since the discs are looselymounted on the shaft 141 and since the discs have appreciable radius,the slightest grazing contact between the back of the advancing sheetand the discs sufices to rotate the discs. Since the sheet does not haveto overcome sliding friction at the region of entry, the sheet, evenwhere made of extremely light paper stock, is free to pass upwardly intothe fixing region. it is to be particularly noted that if the leadingedge of the sheet tends to be curled or buckled, such leading edgesimply rides up on the discs without any risk of doubling back uponitself. T he rollers project slightly beyond the wires forming the guide7th; so that the leading edge of the sheet is certain to clear the lowerend of the guard.

Moreover, any small amount of toner which may be pushed up by theleading edge of the sheet upon passing through the developing unit, andwhich tends to collect upon the discs, cannot increase friction as wherestationary guide wires are employed.

Further in accordance with the invention outlet guides are provided atthe upper end of the fixing region in the form of thin plates of metalsecured to the heat sink memher 160a and presenting guiding edges whichare angled inwardly and upwardly thereby to guide the sheet into the nipof the expeller rollers 36a, 37a. As shown in FIG. 9, these outletguides, indicated at 150, are in the form of angles having an anchoringportion 151 and a projecting portion 152 which is cut at an angle todefine the angled guide edge 153. Similarly to the earlier embodiment,the face of the sheet is clear of any guiding means in the region ofhigh temperature. Stated in other words, by limiting the effectiveguiding edge at the face of the sheet to the region of the exit there isno possibility of contact with the face of the sheet until after thetoner thereon has been fixed in place by heat and cooled below the pointwhere it is capable of being smeared. Moreover, because of the intimatethermal coupling between the guide members 150 and the heat sink andsince the guide members are in the path of the cooling air blow from theupper vent 105, the members are maintained at a safely low temperature,i.e., at a tempertaure that is below that which might cause remelting ofthe toner. It is found that the present arrangement, by delaying anycontact with the face of the sheet until the last possible moment, andby insuring that the guiding means which does contact the base of thesheet is at a low temperature, any possibility of vertical streaks onthe face of the sheet, is avoided. While the number of outlet guides 150may be varied without departing from the present invention, we prefer,in a practical oifice machine to employ a total of six.

In accordance with one of the other features of the present invention aseries of guide' wires are provided at the expeller rollers for guidingthe sheet into the nip, and completely through the expeller rollers,with the upper ends of the wires terminating in a curved deflector sothat the sheets are directed horizontally onto a receiving tray or othersuitable receptacle. More specifically, a final guide member is providedin the form of a grid consisting of spaced wires, with the wires beingreceived and recessed in registering grooves formed in one of theexpeller rollers. Thus, referring to FIGS. 8 and 10 of the drawings, theguide consists of a set of wires 161) secured, by welding or the like,to an upper header 161 and a lower header 162. The headers are securedin any desired fashion, for example, to the side plates of the machine.For accommodating the wires, the expeller roller 36a is formed with aplurality of grooves 165. Preferably the wires are angled as shown, in ashallow herringbone pattern, the width of the individual grooves beingsuflicient to insure lateral clearance for the angled wires. The planeof the final guide wires 16% is preferably angled with respect to theplane of tangency between the expeller rollers, intersecting such planeof tangency along a line which is spaced above the roller axis. Thus,referring to FIG. 8 the outlet guide member bears an angle to the planeof tangency as indi cated at b and which may be on the order of 10 to 30with intersection at the line or locus 167 on the downstream side. Sucharrangement, it is found, absolutely insures the guiding of the leadingedge of the sheet into the nip regardless of the curl or condition ofthe leading edge. After the sheet passes through the nip, engagementoccurs along the line 167, with the leading edge of the sheet beingguided rearwardiy along the curved portion of the guide indicated at 163and with the sheet being deposited in the tray 31 (see FIG.' 1) at thetop of the machine for removal by the operator.

It will be apparent from the above that the present fixing unit isreliable, foolproof and safe in operation under all conditions which maybe encountered in a business office. The unit may be constructed of aminimum of simply formed parts, with the larger parts being in the formof low cost aluminum extrusions minimizing the cost of fabrication andassembly. The unit is capable of operating over long periods of timewith no maintenance except occasional renewing of the lamp.

We claim as our invention:

1. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means for advancingthe sheet along a fixing plane, a longitudinal radiant lamp spaced fromthe fixing plane and at right angles to the direction of the movement ofthe sheet, a generally C-shaped reflector surrounding the lamp andextending to within a short distance of the fixing plane, said reflectorbeing of good conducting metal and of substantial thickness, an air ductadjacent the reflector, fins thermally coupled to the reflector andextending into the air duct, the reflector surface lying in the locus ofan ellipse with the lamp at one focus and with the fixing plane ear theother so that the radiant energy is concentrated at the fixing plane, amirror arranged directly in front of the reflector and on the oppositeside of the fixing plane, an air duct adjacent the mirror, finsthermally coupled to the mirror and extending into the adjacent airduct, and a blower for supplying both of said ducts.

2. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means for advancingthe sheet along a fixing plane, a longitudinal radiant lamp spaced fromthe fixing plane and at right angles to the direction of the movement ofthe sheet, a longitudinal reflector surrounding the lamp and extendingto within a short distance of the fixing plane, said reflector being ofgood conducting metal and of substantial thickness, an air duct adjacentthe reflector, and fins thermally coupled to the reflector and extendinginto the air duct for constantly maintaining the reflector at arelatively cool temperature, the reflector surface lying in the locus ofan ellipse with the lamp at one focus and with the fixing plane near theother so that the radiant energy is concentrated at the fixing plane.

3. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means for advancingthe sheet along a fixing plane, a longitudinal radiant lamp spaced fromthe fixing plane and at right angles to the direction of the movement ofthe sheet, a longitudinal reflector surrounding the lamp and extendingto Within a short distance of the fixing plane, said reflector being ofgood conducting metal and of substantial thickness, an air duct adjacentthe reflector and thermally coupled thereto for con-tsantly maintainingthe reflector at a relatively cool temperature, the reflector surfacelying in the locus of an ellipse with the lamp at one focus and with thefixing plane at the other so that the radiant energy is concentrated atthe fixing plane, and means for positionally adjusting the reflector andthe lamp contained therein relatively toward and away from the fixingplane thereby to altlljust the width of the band of radiation applied tothe s eet.

4. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means for advancingthe sheet along a fixing plane, a longitudinal radiant lamp spaced fromthe fixing plane and at right angles to the direction of the movement ofthe sheet, a longitudinal reflector surrounding the lamp and extendingto within a short distance of the fixing plane, cooling means forconstantly maintaining the reflector at a safe temperature, thereflector surface lying in the locus of an ellipse with the lamp at onefocus and with the fixing plane near the other so that the radiantenergy is concentrated at a band extending along the fixing plane, aheat reflecting surface on the opposite side of the fixing plane for thesaid lamp, and sheet guiding means in the form of narrow guiding edgesspaced side by side on the opposite sides of the fixing plane, theguiding edges at the face of the sheet being spaced away from said bandso that the face of the sheet is engaged by the guiding edges only atregions of reduced temperature.

5. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means for advancingthe sheet along a fixing plane, a radiant heat lamp spaced from thefixing plane and extending longitudinally at right angles to thedirection of movement of the sheet, a longitudinal reflector surroundingthe lamp for focusing the radiant energy on the fixing plane, thereflector being formed of good conducting metal and of massive crosssection, and a heat sink thermally coupled to the reflector for keepingits temperature at a safe level during the time that the heat lamp isenergized and regardless of whether a sheet is passing through thefixing plane, heat absorbing walls integrally formed along the edges ofthe reflector for thermal coupling to the heat sink and lying in a planeparallel to the fixing plane, and a series of guide wires oriented inthe direction of movement of the sheet and interposed between the fixingplane and the reflector.

6. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in .place by heat, the combination comprising means for guidingthe sheet along a fixing plane, a lamp and reflector assembly adjacentthe fixing plane, said assembly including a longitudinally extending airduct and a reflector secured to the wall of the air duct and in goodthermal coupling there with, said reflector having a C-shaped recessincluding a heat lamp extending longitudinally therein so that heat isfocused in a narrow band upon the fixing plane, means defining an airduct on the frame having a mouth in register with said longitudinalduct, means for moving air through the duct, and means for hingedlymounting the lamp and reflector assembly for swinging movement about ahorizontal axis so that the assembly may be swung outwardly away fromthe fixing planeto move said longitudinal duct out of a condition ofregister and to expose said reflector for servicing of the heat lamp.

7. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising a frame, a means inthe frame for conducting a sheet along a fixing plane, a lamp andreflector assembly adjacent said fixing plane and extending transverselywith respect to the direction of movement of the sheet, said lamp andreflector assembly having a reflector recess and a heat lamp mountedtherein, said lamp and reflector assembly being movably mounted on theframe of the machine and having cam adjusting means coupled to the framefor adjusting the assembly toward and away from the fixing plane so thatradiant energy is focused on the fixing plane, said adjusting meansincluding engaging elements disengageable upon slight bodily movement ofthe lamp and reflector assembly at right angles to the direction ofadjustment sothat the elements may be disengaged and the assembly movedoutwardly for servicing of the lamp while maintaining the setting of theadjustment.

8. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising a frame meansincluding a pair of expeller rollers on the frame for conducting thesheet along a fixing plane, a lamp and reflector assembly adjacent saidfixing plane and extending transversely with respect to the direction ofmovement of thesheet, said lamp and reflector assembly having areflector recess and a heat lamp mounted therein, a heat confiningmember opposite the reflector, longitudinally extending air ducts havingmeans providing thermal coupling to the air therein, a blower forsupplying air to the air ducts, at least one of said ducts having alongitudinally extending vent along its upper edge for discharging airtoward said expeller rollers.

9. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means defining afixing region having an inlet and an outlet, a source of radiant heatextending transversely along one side of the fixing region, andextensive heat confining and reflecting member on the other side of saidfixing region and extending parallel to said source of radiant heat,means for transportintg a developed but unfixed sheet through said inletand into the fixing region with the back of the sheet facing the sourceof radiant heat and with the front of the sheet facing the reflectingmember, a pair of driven expeller rollers at the outlet, a first guidingmeans consisting of a plurality of laterally spaced guiding elementsinterposed between the back of the sheet and the source of radiant heatfor defining a certain minimum spacing between the source and the backof the sheet, and a second guiding means consisting of a plurality ofguiding elements interposed between the refiecting surface and the frontof the sheet, said second guiding means being so constructed andarranged as to be in proximity to the sheet only during the terminalportion of the path of travel through the firing region and just aheadof the nip of the expeller rollers and out of proximity to the sheet inthe fixing region thereby to insure freedom from contact with the faceof the sheet during the high temperature portion of its path of travelthrough the fixing region.

10. In a fixing unit for a copy sheet in a photocopy machine having apowder image thereon including a binding agent capable of fixing thepowder in place by heat, the combination comprising means defining afixing region having an inlet and an outlet, a source of radiant heatextending transversely along one side of the fixing region, means fortransporting a developed but unfixed sheet through said inlet and intothe fixing region with the back of the sheet facing the source ofradiant heat, a pair of expeller rollers at the outlet, guiding meansfor guiding the back of the sheet and insuring that the sheet ismaintained at a predetermined minimum spacing from the source of radiantheat during its path of travel from inlet to outlet, face guiding meanspositioned opposite the face of the sheet immediately ahead of theexpeller rollers for guiding the sheet into the nip of the expellerrollers while leaving the face of the sheet in the remainder of thefixing region free of guiding contact, and means for directing a blastof cooling air upon the sheet and face guiding means just ahead of thenip of the expeller rollers.

References Cited by the Examiner UNITED STATES PATENTS 2,639,364 5/53Doyle 219-201 2,807,703 9/57 Roshon 25065 2,807,704 9/57 Allen et a1.250-65 3,005,081 10/61 Kordes et a1. 2l9-473 3,053,962 9/62 Cerasani etal 2l9388 3,076,083 1/63 Codichini et a1 2l9--2l6 FOREIGN PATENTS264,814 12/27 Great Britain. 278,012 1/52 Switzerland.

RICHARD M. WOOD, Primary Examiner.

8. IN A FIXING UNIT FOR A COPY SHEET IN A PHOTOCOPY MACHINE HAVING APOWDER IMAGE THEREON INCLUDING A BINDING AGENT CAPABLE OF FIXING THEPOWEDER IN PLACE BY HEAT, THE COMBINATION COMPRISING A FRAME MEANSINCLUDING A PAIR OF EXPELLER ROLLERS ON THE FRAME FOR CONDUCTING THESHEET ALONG A FIXING PLANE, A LAMP AND REFLECTOR ASSEMBLY ADJACENT SAIDFIXING PLANE AND EXTENDING TRANSVERSELY WITH RESPECT TO THE DIRECTION OFMOVEMENT OF THE SHEET, SAID LAMP AND REFLECTOR, ASSEMBLY HAVING AREFLECTOR RECESS AND A HEAT LAMP MOUNTED THEREIN, A HEAT CONFININGMEMBER OPPOSITE THE REFLECTOR, LONGITUDINALLY EXTENDING AIR DUCTS HAVINGMEANS PROVIDING THERMAL COUPLING TO THE AIR THEREIN, A BLOWER FORSUPPLYING AIR TO THE AIR DUCTS, AT LEAST ONE OF SAID DUCTS HAVING ALONGITUDINALLY EXTENDING VENT ALONG ITS UPPER EDGE FOR DISCHARGING AIRTOWARD SAID EX PELLER ROLLERS.